Tube stretching machines



July 26, 1955 SINGER ET AL 2,713,801

TUBE STRETCHING MACHINES Filed Aug. 15, 1951 3 Sheets-Sheet l INVENTOR ,fiiiz, Sill er il hll/z jfwgse,

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ATTORNEY United States Patent i TUBE STRETCHING MACHINES Fritz Singer, Starnberg (Oberbayem), and Fritz Haase, Goppingen (Wurttemberg), Germany, assignors, by mesne assignments, to Tube Reducing Corporation, Wallington, N. J., a corporation of Delaware Application August 13, 1951, Serial No. 241,637

Claims priority, application Germany October 10, 1948 7 Claims. (Cl. 80-12) This invention relates to tube stretching machines of the kind in which the reduction in wall thickness of a metal tube is effected by the action of a reciprocatory die, the tube being fed forward over a plug-mandrel the diameter of which is larger than the inner diameter of the tube in a step-by-step manner alternately with the movement of the die.

The object of the invention is to enable the frictional resistance between the die and tube to be minimized, otherwise than by the use of a lubricating substance.

The invention comprises the combination of a reciprocatory headstock, and a die formed by a plurality of peripherally grooved rollers or oscillatory segments arranged to embrace the tube.

The invention also comprises the combination with the means specified in the preceding paragraph of means for enabling a smooth outer surface to be formed on the tube.

in the accompanying drawings:

Figure 1 is a sectional side elevation, and Figure 2 a plan of a portion of a tube stretching machine embodying the invention.

Figure 3 is a sectional front elevation of the headstock and roller die.

Figure 4 is a section on the line 4-4 of Figure 2.

Figure 5 is a fragmentary view showing in detail and to a larger scale than Figure 4, one of the thrust links for imparting angular movements to the headstock.

Figure 6 is a diagram illustrating a modified embodiment of the form of the invention shown in Figure 1, and Figure 7 is a diagram illustrating the relative disposition of the two sets of roller-dies shown in Figure 6.

Figure 8 is a part sectional side elevation and Figure 9 is a part sectional front elevation of the headstock provided with an oscillatory-segment die.

Referring to Figure l, the part of the tube stretching machine thereshown, comprises a reciprocatory slide a mounted on a bed b and carrying a headstock c. The slide a is reciprocated by a connecting rod a which is actuated by a rotary crank (not shown).

On the headstock c is mounted the die which comprises a plurality of rollers e (instead of the usual solid die having therein a hole corresponding to the required external diameter of the finished tube). In this example three rollers are provided and arranged as shown in Figure 3. Each roller is formed with a circumferential groove and the rollers are so mounted as to form between them a circular pass corresponding in diameter to the required external diameter of the tube. The rollers are carried on the headstock by spindles f and are freely mounted on the spindles.

The plug mandrel which lies within the tube is represented by 4, and is fixedly secured in the position shown. The tube to be treated is represented by 5.

The action of the machine is essentially similar to that in which a solid die is used. The tube is intermittently fed forward over the plug of the mandrel the diameter of which is larger than the inner diameter of the tube 2,713,801 Patented July 26, 1955 in the direction of the arrow (Figure l), and after each feed movement the slide a is advanced in the same direction to effect the required reduction of thickness of the portion of the tube wall in contact with the mandrel plug. It will be understood that whereas the slide, together with the headstock and roller die move with a short reciprocatory motion, the tube is moved only in the one direction in a step-by-step manner.

The essential feature of novelty of the invention resides in the combination with the headstock of a roller-die instead of the conventional solid die. By the use of a die formed by rollers, the normal and deleterious frictional resistance between the die and tube is greatly reduced.

An undesired consequence of the use of a roller-die is that minute longitudinal ridges may be formed on the tube surface at positions coinciding with the abutting edges of the rollers. But this may readily be obviated by imparting intermittent angular movements to the headstock, so as to cause successive actions of the die rollers to obliterate the ridges formed in the preceding action.

In the example shown in Figures 1-5, the headstock c is rotatably mounted on the slide a, and is embraced by two pairs of gripping jaws g. Each pair of jaw parts are hingedly connected at h, and at their free ends are interconnected by a pin 1' loaded by a spring j. On the slide a is pivotally mounted a two-arm lever k, the arms of which are mutually inclined as shown in Figure 2, and the ends of the lever are connected to the jaws through thrust rods in. Also on the bed of the machine is mounted a roller 11 for actuating the lever. One end of each thrust rod is connected to the lever k by a swivel joint 0. The connection with the associated jaws is effected by a telescopic coupling p and swivel joint q. On the rod between the parts 0, p is mounted a strong spring r (Figure 5). Starting with the headstock in the position shown in Figure 2, the return movement of the slide (to the right) causes the thrust rods to receive endwise movement in opposite directions. The effect of this movement is to release the right hand gripper, and almost simultaneously the left hand gripper is caused to grip the headstock, this action being followed by compression of the associated spring. When the slide carries the roller-die clear of the tube, the stored energy of the spring imparts a small angular movement to the headstock. During the forward movement of the slide, the left hand gripper is released and the right hand gripper brought into action. When the slide reaches the end of its forward movement and the roller-die has completed its action on the tube, the stored energy of the spring of the right hand gripper imparts a further small angular movement to the headstock.

By progressively rotating the headstock as above described the position of the tube relatively to the die is so varied that the ridges formed on the tube in one action of the die are obliterated in the next action.

In practice it has not proved necessary to impart angular movement to the headstock towards the ends of both the forward and backward movement of the headstock. In stretching tubes of very hard alloys extremely strong springs r would be necessary to effect angular movement of the headstock at the end of the forward stroke although the tube is not in contact with the mandrel-plug at that point due to the fact that the forward end of the mandrel-plug is shaped conical. To avoid these inconveniences it is only necessary to set the right hand gripper out of work.

As an alternative means for obliterating the ridges on the tubes, the arrangement shown in Figure 6 may be used. In this example the headstock c is fixedly mounted on the slide, and a smoothing roller-die e is mounted in a housing t which is fixed to the bed 15 at a position in advance t) of the slide. The two dies are disposed in the relative angular positions shown in Figure 7, so that any ridges produced by the die e can be removed by the smoothing die 2 In still another arrangement two roller-dies may be mounted on the headstock c in the angular relationship shown in Figure 7. One of the dies effects the normal tube-thinning action, and the other serves to smooth the outer surface of the tube.

When the stretching operation is to be performed on hard metal tubes, and where the pressure to be exerted by the die is very heavy, an excessive load may be imposed on the spindles of the die rollers. In this case, it is preferable to employ a die formed by oscillatory segments which can be adequately supported by trunnions of ample diameter. An example of this alternative is shown in Figures 8 and 9. In the headstock c are mounted three die sigments a shaped and disposed to form a circular pass for the tube, and each segment is supported in the headstock by trunnion v. To maintain the segments in proper relationship a toothed quadrant w is forced on each, and each quadrant engages a rack x loaded by.

springs y. The racks x extend through and can slide relatively to an annulus 2 which is rotatably mounted on a bracket 3 secured to the bed b of the machine. The free ends of the racks x are guided in the headstock on guideblocks 1 mounted in the headstock. In this example the headstock is intermittently rotatable as above described for enabling any ridges formed by the die segments on the tube to be obliterated.

By the present invention, the action of tube drawing machines of the kind specified can be greatly improved.

We claim:

1. A tube stretching machine including a machine bed, a slide mounted on said bed for reciprocating motion, a headstock rotatably mounted on the slide, a die mounted on the headstock and comprising a plurality of arcuate working surfaces arranged to embrace a tube, meansoperatively related to the slide for imparting angular movement to the headstock, and means on the bed for engagement by the first named means to actuate the same.

2. A tube stretching machine including in combination a machine bed; a rotatable headstock mounted for recip rocating movement relative to said bed; a die comprising oscillatory segments for embracing a tube; trunnion means in the headstock supporting the said segments; rack and quadrant means associated with each segment for maintaining the segments in proper relationship; carrier means mounted on the machine bed for carrying the rack means; and means for effecting intermittent r0- tation of the headstock.

3. A tube stretching machine having in combination a machine bed; a slide adapted to have reciprocating motion mounted on said bed; a headstock rotatably mounted on said slide; means for intermittently rotating the headstock including gripping jaws embracing the headstock, lever means pivotally mounted on the slide, roller means mounted on the machine bed for actuating the lever means, thrust rods connected to said gripping jaws and to said lever means; and die means comprising a plurality of rotatable curved working surfaces for embracing a tube, said die means being mounted on the headstock.

4. A tube stretching machine comprising a machine bed; a slide mounted for reciprocation thereon; a headstock rotatably mounted on the slide; a die comprising a plurality of grooved rollers mounted on the headstock; means carried by the slide for imparting intermittent angular movements to the headstock and means on the bed for engagement by the first named means to actuate the same.

5. A tube stretching machine including in combination, a machine bed, a slide reciprocatingly mounted on the bed, a headstock rotatably mounted on the slide, a die mounted on the headstock and having a plurality of rotatably mounted working surfaces; and means for imparting intermittent angular movements to the headstock including means mounted on the slide responsive to actuation by means mounted on the bed.

6. A tube stretching machine including in combination, a machine bed, a slide mounted reciprocatingly thereon, a headstock rotatably mounted on the slide, a die carried by the headstock and having a plurality of rollers arranged to embrace a tube; and means for imparting intermittent angular movements to the headstock including means for gripping the headstock, lever means pivotally mounted on the slide, means mounted on the machine bed for actuating the lever means, and thrust rod means in swivel connection with said gripping means and said lever means.

7. The tube stretching machine set forth in claim 2 in which the carrier means for carrying the rack means includes a bracket, an annulus rotatably mounted on the bracket, the rack means extending through and slidable relatively to the annulus and guided in guide blocks mounted in the interior of the headstock.

References Cited in the file of this patent UNITED STATES PATENTS 2,161,065 Krause June 6, 1939 2,432,566 Findlater Dec. 16, 1947 FOREIGN PATENTS 149,862 Austria Feb. 15. 1937 

